A resonator fiber optic gyroscope (RFOG) senses rotation rate by detecting the difference in clockwise (CW) and counter-clockwise (CCW) resonance frequencies of an optical fiber ring resonator. The RFOG shows promise to meet the needs of many navigation and inertial stabilization markets. The resonance frequencies are detected by probing the ring resonator with frequency or phase modulated laser light. When the average laser frequency is on resonance, the resonator output signal at the modulation frequency will ideally be zero. If the laser frequency slightly deviates from the resonance frequency, the resonator output will have a nonzero signal amplitude at the modulation frequency. The sign of the signal relative to the modulation depends on which side of resonance the laser frequency has deviated. To detect deviations in laser frequency relative to the resonance frequency, phase sensitive demodulation is employed.